Using Ground-Source Heat Pump Systems for Heating/Cooling of Buildings

This chapter mainly presents a detailed theoretical study and experimental investigations of ground-source heat pump (GSHP) technology, concentrating on the ground-coupled heat pump (GCHP) systems. A general introduction on the GSHPs and its development, and a description of the surface water (SWHP), ground-water (GWHP), and ground-coupled heat pumps are briefly performed. The most typical simulation and ground thermal response test models for the vertical ground heat exchangers (GHEs) currently available are summarized. Also, a new GWHP using a heat exchanger with special construction, tested in laboratory, is well presented. The second objective of the chapter is to compare the main performance parameters (energy efficiency and CO2 emissions) of radiator and radiant floor heating systems connected to a GCHP. These performances were obtained with site measurements in an office room. Furthermore, the thermal comfort for these systems is compared using the ASHRAE Thermal Comfort program. Additionally, two numerical simulation models of useful thermal energy and the system coefficient of performance (COPsys) in heating mode are developed using the TRNSYS (Transient Systems Simulation) software. Finally, the simulations obtained in TRNSYS program are analysed and compared to experimental measurements

Experimental and analytical performance investigation of air to air two phase closed thermosyphon based heat exchangers

In recent years, the use of wickless heat pipes (thermosyphons) in heat exchangers has been on the rise, particularly in gas to gas heat recovery applications due to their reliability and the level of contingency they offer compared to conventional heat exchangers. Recent technological advances in the manufacturing processes and production of gravity assisted heat pipes (thermosyphons) have resulted in significant improvements in both quality and cost of industrial heat pipe heat exchangers. This in turn has broadened the potential for their usage in industrial waste heat recovery applications. In this paper, a tool to predict the performance of an air to air thermosyphon based heat exchanger using the ε-NTU method is explored. This tool allows the predetermination of variables such as the overall heat transfer coefficient, effectiveness, pressure drop and heat exchanger duty according to the flow characteristics and the thermosyphons configuration within the heat exchanger. The new tool's predictions were validated experimentally and a good correlation between the theoretical predictions and the experimental data, was observed. © 2014 Elsevier Ltd. All rights reserved

Analysis of a district energy system containing thermal energy storage and heat pumps

Tese de mestrado integrado em Engenharia da Energia e do Ambiente, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2017No contexto de atingir as metas estabelecidas até 2050 para a redução da emissão de gases de efeito de estufa, as redes urbanas de energia são já consideradas uma solução provada. Isto deve-se essencialmente ao facto de estas possibilitarem recuperar energia que seria de outra forma desperdiçada. Para além disso, possibilitam a integração de diferentes fontes de energia renovável, ou outras tecnologias, como é o caso de armazenamento térmico de energia. Quando presente, armazenamento de energia térmica confere maior flexibilidade, bem como maior segurança energética e pode ser usado para otimizar o equipamento responsável pela produção de energia térmica, como por exemplo bombas de calor. O principal objetivo deste projeto é estudar a influência da introdução de armazenamento de energia térmica de curta duração numa rede urbana de energia, em que o abastecimento de calor é suprido por uma combinação de armazenamento de energia térmica sazonal e bombas de calor. Em particular, pretende-se analisar de que forma pode o armazenamento de curta duração, que consiste num tanque de água, ser usado para deslocar a produção de calor (carga térmica), de períodos de cheia ou ponta, para períodos de vazio, e quantificar as consequências desta estratégia (load shifting) na produção de energia térmica e consumo de eletricidade. Para que isto seja possível, o consumo de energia relacionado com aquecimento e arrefecimento de um grupo de edifícios é determinado usando um modelo implementado em Modelica, e a análise dos sistemas de energia é feita através de um modelo analítico, implementado em Matlab. Os resultados obtidos mostram que a introdução de armazenamento térmico de curto prazo, permitiu deslocar parte da carga térmica de períodos de pico, para períodos de vazio. Isto levou a uma redução significativa (11.5% a 37.5%) nos custos individuais de eletricidade para os consumidores de calor, que foram determinados com base nos preços de mercado de eletricidade holandês (EPEX), e em tarifas de distribuição e transmissão. Paralelamente, verificou-se um aumento na produção total de calor (~ 7%), principalmente devido a maiores perdas térmicas face ao sistema sem armazenamento de curta duração. No entanto, a eficiência global das bombas de calor (COP) também aumentou (~ 14%), o que resultou ainda assim num menor consumo global de eletricidade (~ -13%), apesar da maior produção de energia.In the context of meeting the targets set by 2050 for reducing greenhouse gas emissions, District Energy (DE) systems are considered to be a proven solution. This is essentially due to their ability to re-use energy that would otherwise be wasted, and its compatibility with a variety of other technologies, such as Thermal Energy Storage (TES) and renewable energy sources. When available, thermal energy storage provides greater flexibility, reliability, as well as energy security and it can be used to optimize equipment responsible for thermal energy production, as for instance, heat pumps. The main objective of this project is to study the influence of the introduction of short-term thermal storage in a DE, where heat and cold requirements are supplied by a combination of seasonal TES and heat pumps. To be specific, the focus is to analyze to what extent can short-term TES be used to shift the heat pumps electrical heating loads, from peak to off-peak periods, and quantify the influence of this strategy on energy production and electricity consumption. In order to do this, space heating and cooling demand data regarding a group of buildings is determined in Dymola/Modelica, and the energy systems performance is evaluated by using an analytical MATLAB model. The results obtained show that the introduction of short-term storage allowed to shift some of the thermal load from peak to off-peak periods. This operation led to a significant reduction in the individual electricity costs for the heat consumers (11.5% to 37.5%), which were determined based on electricity prices from the Dutch EPEX day-ahead spot market. Regarding electricity consumption and total heat production, it was noticed that the introduction of short-term storage led to an increase in the total heat output from heat pumps (~7%), mainly due to higher thermal losses. However, the global heat pumps coefficient of performance (COP) also increased (~14%), which resulted in less electricity consumption (~-13%), despite of the higher heat production

Energy: A continuing bibliography with indexes, issue 13

This bibliography lists 1036 reports, articles, and other documents introduced into the NASA scientific and technical information system from January 1, 1977 through March 31, 1977

RELATED, A FLEXIBLE APPROACH TO THE DEPLOYMENT AND CONVERSION OF DH NETWORKS TO LOW TEMPERATURE, WITH INCREASED USE OF LOCAL SOLAR SYSTEMS

District heating (DH) systems are key systems for the de-carbonization of heating energy in European Cities. In order to allow for this transition, while guaranteeing competitive energy costs, conversion of DHs is required. DH operation temperature needs to be reduced in order to increase the performance of renewable systems and operation criteria needs to be adopted for the introduction of weather-dependent, distributed heat sources such as solar systems. This paper presents the RELaTED decentralized Ultra-Low Temperature DH network scheme, and its adaptation to several operational schemes such as new and existing DH networks, with different levels of complexity. Transitory phases in the conversion process are discussed.European Commission's H2020, 768567, RELaTE